In the exploration for oil and gas well, due to the limitations from factors such as the ground conditions, the subsurface distribution of oil reservoir, etc., it is necessary to change and control the drilling direction and advance the drilling device along a predetermined trace, such that the drilling bit can reach the oil and gas reservoir, where oil and gas may be explored. The wells, such as conventional directional wells, horizontal wells, branch wells, multilateral wells, 3D bypass staggered wells, etc., all need the rotary steering technology.
Recently, with the development of the petroleum and natural gas industry, the demand on oil-gas exploration and production has been increased, thus higher requirements are imposed on the rotary steerable systems.
The traditional rotary steerable systems may be divided into two types: push-the-bit rotary steerable systems and point-the-bit rotary steerable systems. The push-the-bit rotary steerable systems have high build-up rates, but the traces of well bore thereof are not smooth and the well walls are also relatively coarse. The point-the-bit rotary steerable systems are able to form relatively smooth traces of well bore and relatively even well walls, but have low build-up rates.
The movable range of the drill pipe of the existing rotary steerable system is small, and the steering precision is low.
The steering effects of the existing rotary steerable system are much subjected to the conditions of well walls, and an uneven well wall may promote vibrations, further causing a more unsmooth trace of well bore.
Additionally, the existing rotary steerable system has low reliability and short service life, and is vulnerable to impurities like dinas, which may cause the system to operate abnormally, thus the maintenance cost is increased sharply.
Accordingly, there is a need to provide a new rotary steerable system and a method for steering a drilling device, in order to solve the above-mentioned technical problems.